Transmission screen and projection display

ABSTRACT

A transmission screen has a refraction total reflection Fresnel lens plate, a stray light eliminating plate, and an image display plate. The stray light eliminating plate has a condensing lens array and black stripes. The array has unit lenses arranged at an incident plane of the transparent substrate in a periodic structure in an up-and-down direction. The black stripes have transparent sections placed near condensing light points of the unit lens and opaque sections around the condensing light points of the unit lenses. The sections are alternately arranged at the outgoing plane of the transmission substrate in a periodic structure in an up-and-down direction. The image display plate has lenticular lenses in which unit lenses are arranged in a periodic structure in a horizontal direction at an incident plane of the transmission substrate of a scattering characteristic capable of scattering light fluxes.

TECHNICAL FIELD

The present invention relates to a transmission screen capable ofpreventing a deterioration of a display characteristic generated thereincaused by an ineffective flux of light, and also relates to a projectiondisplay device using the transmission screen.

BACKGROUND ART

A description will now be given of problems of conventional transmissionscreens using various kinds of Fresnel lens means such as a refractionFresnel lens plate, a total reflection Fresnel lens plate, and arefraction total reflection Fresnel lens plate by referring to FIG. 1 toFIG. 3.

FIG. 1 is a diagram showing a configuration and operation of aconventional refraction Fresnel lens plate. FIG. 1 shows a shape of across section of the conventional refraction Fresnel lens plate in whicha refraction Fresnel plane is formed at an incident side of a projectedlight flux. In FIG. 1, reference character 110A is a refraction Fresnellens plate (as refraction Fresnel lens means), reference number 111denotes a refraction inclined plane (as a refraction Fresnel plane), 112indicates an ineffective facet plane (as a refraction Fresnel plane),and 115 designates an outgoing plane. Reference character n designates anormal of the refraction Fresnel lens plate 110A (or the outgoing plane115).

Reference number 150 designates a projected light flux of the refractionFresnel lens plate 110A, 152 denotes an ineffective flux of light, 153indicates an effective flux of light. The refraction Fresnel lens plate110A comprises the refraction inclined plane 111 and the ineffectivefacet plane 112 adjacent to the plane 111, which are formed in aperiodic structure.

Next, a description will now be given of the operation.

The projected light flux 150 enters in an angle to the normal n of therefraction Fresnel lens plate 110A. A part of the light flux 150 isrefracted (in optical action) by the refraction inclined plane 111toward the direction of the normal n, and outputs as an effective fluxof light 153 from the outgoing plane 115 of the refraction Fresnel lensplate 110A.

On the other hand, the remaining part of the light flux 150 is refracted(in optical action) at the ineffective facet plane 112 and becomesineffective flux of light 152.

The ineffective flux of light 152 inclines to the normal n, a partthereof outputs through the outgoing plane 115, and another part thereofis reflected at the outgoing plane 115. The ineffective flux of light152 reflected at the outgoing plane 115 enters the refraction inclinedplane 111 or the ineffective facet plane 112 again, which form therefraction Fresnel lens plate 110A. The refraction and the reflection ofthe ineffective flux of light 152 are repeated between the refractioninclined plane 111 or the ineffective facet plane 112 and the outgoingplane 115.

The effective flux of light 153 in the above light fluxes is a normalimage light. The ineffective flux of light 152 causes the generation ofa double image and a ghost image to display spots and line images atincorrect display positions.

FIG. 2 is a diagram showing the explanation of the structure and theoperation of the conventional total reflection Fresnel lens plate. FIG.2 shows the shape of the cross section of the total reflection Fresnellens plate in which the total reflection Fresnel plane is formed at theincident side of the projected light flux. In FIG. 2, referencecharacter 110B is the total reflection Fresnel lens plate (totalreflection Fresnel lens means), reference number 113 denotes a totalreflection inclined plane (total reflection Fresnel plane), 114indicates a transmission inclined plane (total reflection Fresnelplane), 115 denotes an outgoing plane, and n indicates the normal of thetotal reflection Fresnel lens plate 110B (or the outgoing plane 115).

Reference number 150 designates a projected light flux to the totalreflection Fresnel lens plate 110B, 151 denotes an effective flux oflight, and 152 designates a deviated flux of light (as the ineffectiveflux of light).

The total reflection Fresnel lens plate 110B is made up of a combinationof the total reflection inclined plane 113 and the transmission inclinedplane 114 adjacent to the total reflection inclined plane 113 in aperiodic structure.

Next, a description will now be given of the operation. The projectedlight flux 150 enters at an angle to the normal n of the totalreflection Fresnel lens plate 110B, apart thereof is refracted (inoptical action) and then reflected (in optical action) at thetransmission inclined plate 114 toward the normal n at the totalreflection inclined plane 113, and then outputs as the effective flux oflight 151 through the outgoing plate 115 of the total reflection Fresnellens plate 110B.

On the other hand, the remaining part of the projected light flux 150becomes a deviated flux of light 152, not reflected at the totalreflection inclined plane 113.

The deviated flux of light 152 is inclined in direction to the normal n.A part thereof is output through the outgoing plane 115, another partthereof is reflected at the outgoing plane 115. Then, the deviated fluxof light 152 reflected at the outgoing plane 115 enters again into totalreflection inclined plane 113 or the transmission inclined plane 114which forms the total reflection Fresnel lens plate 110B.

The refraction and the reflection of the deviated flux of light 152 arerepeated between the total reflection inclined plane 113 or thetransmission inclined plane 114 and the outgoing plane 115.

The effective flux of light 151 in the above light fluxes is the normalimage light. The deviated flux of light 152 causes the generation of adouble image and a ghost image which display spots and line images atincorrect display positions.

FIG. 3 is a diagram showing a configuration and operation of aconventional refraction total reflection Fresnel lens plate. FIG. 3shows the configuration of the refraction total reflection Fresnel lensplate in which both the refraction Fresnel plane and the totalreflection Fresnel plane are formed at the incident plane of theprojected light flux.

In FIG. 3, the same components of the configurations shown in FIG. 1 andFIG. 2 will be referred to with the same reference numbers andcharacters. In FIG. 3, reference character 110C designates therefraction total reflection Fresnel lens (refraction total reflectionFresnel lens means).

Next, a description will now be given of the operation.

The projected light flux 150 enters in an angle to the normal n of therefraction total reflection Fresnel lens plate 110C. The light fluxrefracted at the refraction inclined plane 111 becomes the effectiveflux of light 153 which travels toward the direction of the normal n. Inaddition, the light flux refracted (in optical action) at thetransmission inclined plane 114 and then reflected (in optical action)at the total reflection inclined plane 113 becomes the effective fluxlight 151 which travels to the normal n.

On the other hand, a projected light flux 150 and a projected light flux150, the former is refracted (in optical action) at the ineffectivefacet plane 112 and the latter is refracted (in optical action) and doesnot perform the total reflection at the total reflection inclined plane113, become the ineffective flux of light (as a deviated flux of light)152.

The ineffective flux of light 152 travels towards a direction inclinedrelative to the normal n, and a part thereof outputs through theoutgoing plane 115, and another part is reflected at the outgoing plane115.

The ineffective flux of light 152 reflected at the outgoing plane 115enters again into the refraction inclined plane 111, the ineffectivefacet plane 112, the total reflection inclined plane 113, and thetransmitting inclined plane 114 which form the refraction totalreflection Fresnel lens plate 110C. The refraction and reflection arethen performed for the ineffective flux of light 152 between therefraction inclined plane 111, the ineffective facet plane 112, thetotal reflection inclined plane 113, the transmission inclined plane114, and the outgoing plane 115.

The effective fluxes of light 151 and 153 in the above light fluxes arethe normal image light. The ineffective flux of light 152 often causes adouble image and a ghost image which display a spot and a line image atpositions different from the normal display position.

In the configuration of the conventional transmission screen, alenticular lens plate (omitted from diagrams) is arranged at theoutgoing plane 115 side of the Fresnel lens plate 110A, the totalreflection Fresnel lens plate 110B, the refraction total reflectionFresnel lens plate 110C shown in FIG. 1 to FIG. 3 in order to control ageometric field angle in a horizontal direction and an up-and-downdirection and to make the image.

Because the conventional transmission screen has the configurationdescribed above which generates the effective flux light to contributesthe display of the normal projected image, it is difficult in principleto avoid the generation of the ineffective flux of light which causesthe phenomenon of a double image and a ghost image. Therefore theconventional transmission screen involves a problem in which the doubleimage and the ghost image overlap the normal projected image. Becausethe generation of the double image and the ghost image deteriorates ahigh image quality in display, there is a demand to decrease thegeneration of the double image and the ghost image.

The present invention is provided to solve the above-described problems,and the object of the present invention is to provide a transmissionscreen with a high image quality capable of avoiding any generation ofineffective fluxes of light and displaying the normal projected imageonly using effective fluxes of light.

In addition, another object of the present invention is to provide aprojection display device capable of eliminating any generation of adouble image and a ghost image and of displaying the image with a highquality.

DISCLOSURE OF INVENTION

In carrying out the invention and according to one aspect thereof, thereis provided a transmission screen having Fresnel lens means, stray lighteliminating means, and image display means. The Fresnel lens means has aFresnel surface molded as an incident plane thereof for giving itsoptical action to projected light fluxes and for outputting the lightfluxes through an outgoing plane thereof. The stray light eliminatingmeans eliminates a light flux having only a different angle generatedbased on the optical action of the Fresnel surface. The image displaymeans scatters the light flux from the stray light eliminating means andfocuses the scattered one. It is thereby possible to obtain the effectto provide the transmission screen for eliminating ineffective lightfluxes and displaying only a normal projected image using effectivelight fluxes with a high quality.

In the transmission screen according to the present invention, theFresnel lens means is refraction Fresnel lens means having a refractionFresnel plane formed at the incident plane thereof, and the refractionFresnel plane has refraction inclined planes for refracting lightfluxes, and ineffective facet planes, which are arranged in a periodicstructure. It is thereby possible to obtain the effect to realize ahighly transmission efficiency in an area of small radius of the Fresnellens means.

In the transmission screen according to the present invention, theFresnel lens means is total reflection Fresnel lens means having a totalreflection Fresnel plane formed at the incident plane thereof. The totalreflection Fresnel plane has transmission inclined planes for refractinglight fluxes and total reflection inclined planes for reflecting thelight fluxes refracted at the transmission inclined planes, which arearranged in a periodic structure.

In the transmission screen according to the present invention, theFresnel lens means is refraction total reflection Fresnel lens means hasa refraction total reflection Fresnel plane formed at the incident planethereof. The refraction total reflection Fresnel plane has refractioninclined planes for refracting light fluxes, ineffective facet planes,transmission inclined planes for refracting the light fluxes, and totalreflection inclined planes for reflecting the light fluxes refracted atthe transmission inclined planes, which are arranged in a periodicstructure. It is thereby possible to obtain the effect to realize ahighly transmission efficiency in an area of a small radius of theFresnel lens means.

In the transmission screen according to the present invention, therefraction inclined planes in the Fresnel lens means refract theprojected light fluxes toward a direction approximately parallel to anormal of the outgoing plane of the Fresnel lens means. It is therebypossible to obtain the effect to form the display image of a lightdistribution characteristic of symmetry to the direction of the normalof the transmission screen and to display the display image for anobserver at the center of the transmission screen under the optimumcondition.

In the transmission screen according to the present invention, the totalreflection inclined planes in the Fresnel lens means reflect the lightfluxes refracted at the transmission inclined planes toward a directionapproximately parallel to a normal of the outgoing plane of the Fresnellens means. It is thereby possible to obtain the effect to form thedisplay image of a light distribution characteristic of symmetry to thedirection of the normal of the transmission screen and to display thedisplay image for an observer at the center of the transmission screenunder the optimum condition.

In the transmission screen according to the present invention, therefraction inclined planes in the Fresnel lens means refract theprojected light fluxes toward a direction approximately parallel to anormal of the outgoing plane of the Fresnel lens means. The totalreflection inclined planes in the Fresnel lens means reflect the lightfluxes refracted at the transmission inclined planes toward thedirection approximately parallel to the normal of the outgoing plane ofthe Fresnel lens means. It is thereby possible to obtain the effect toform the display image of a light distribution characteristic ofsymmetry to the direction of the normal of the transmission screen andto display the display image for an observer at the center of thetransmission screen under the optimum condition.

In the transmission screen according to the present invention, theFresnel lens means changes a ratio of a total reflection Fresnel sectionand a refraction Fresnel section, and the total reflection Fresnelsection is composed of the transmission inclined planes and the totalreflection inclined planes and the refraction Fresnel section iscomposed of the refraction inclined planes and the ineffective facetplanes according to a distance measured from a center of its rotation.It is thereby possible to obtain the effect to further increase thetransmission efficiency.

In the transmission screen according to the present invention, the straylight eliminating means has condensing light lens array means and firstblack stripe means. In the condensing light lens array means, unitlenses are arranged at an incident plane of a first transmissionsubstrate in a periodic structure in an up-and-down direction. The firstblack stripe means is composed of transparent sections placed near acondensing light point of each unit lens and opaque sections placed at aperipheral area of the condensing light point of each unit lens, whichare arranged alternately at the outgoing plane of the first transparentsubstrate in aperiodic structure in an up-and-down direction. It isthereby possible to obtain the effect to provide the transmission screencapable of eliminating the ineffective flux of light and of displayingthe normal projected image only using the effective flux of light with ahigh quality.

In the transmission screen according to the present invention, the imagedisplay means is lenticular lens means having the unit lenses arrangedin a periodic structure in a horizontal direction at an outgoing planeof a second transparent substrate having a scattering characteristiccapable of scattering the light fluxes. It is thereby possible to obtainthe effect to scatter the image light fluxes by a simple configurationin order to make the image.

In the transmission screen according to the present invention, the straylight eliminating means has holding transmission substrate for holdingthe first transmission substrate, the condensing light lens array means;and the first black stripe means. It is thereby possible to obtain theeffect to form the stray light eliminating means even if the layer ofeach of the first transmission substrate and the condensing light lensarray means is thin.

In the transmission screen according to the present invention, the straylight eliminating means has the condensing light lens array means andthe first black stripe means, which are molded with a concentric circleshape around a center of rotation of the Fresnel lens means. It isthereby possible to obtain the effect to further exert the function ofthe stray light eliminating means capable of eliminating ineffectiveflux of light.

In the transmission screen according to the present invention, the straylight eliminating means has the condensing light lens array means andthe first black stripe means, which are molded with a periodic structureof a line shape. It is thereby possible to obtain the effect to greatlyrelease the limit from the manufacture of the stray light eliminatingmeans and to display the good image with a low manufacturing cost.

In the transmission screen according to the present invention, the straylight eliminating means has one of the first transmission substratehaving a scattering characteristic and the condensing light lens arraymeans having the scattering characteristic. It is thereby possible toobtain the effect to prevent a deterioration of the projected imagewhich is caused by the image light fluxes based on scintillation.

In the transmission screen according to the present invention, the imagedisplay means has second black stripe means in which transparentsections and opaque sections are arranged at the outgoing plane of athird transparent substrate alternately in a periodic structure in ahorizontal direction, the transparent sections are placed near thecondensing light point of each unit lens in the lenticular lens means,and the opaque sections are placed at a peripheral area of thecondensing light point of each unit lens. It is thereby possible toobtain the effect to eliminate the components in an up-and-downdirection and a horizontal direction and to eliminate the occurrence ofa double image and a ghost image.

In the transmission screen according to the present invention, the straylight eliminating means has transparent sections through which the lightfluxes pass, horizontal louver shaped opaque sections arranged in aperiodic structure in an up-and-down direction between the transparentsections, and up-and-down louver shaped opaque sections arranged in aperiodic structure in a horizontal direction between the transparentsections. It is thereby possible to obtain the effect to eliminate thecomponents in an up-and-down direction and a horizontal direction and toeliminate the occurrence of a double image and a ghost image.

In the transmission screen according to the present invention, the straylight eliminating means has transparent sections through which the lightfluxes pass, and a horizontal louver shaped opaque sections arranged ina periodic structure in an up-and-down direction between the transparentsections. The image display means has second black stripe means in whichtransparent sections and opaque sections are arranged at the outgoingplane of a third transparent substrate alternately in a periodicstructure in a horizontal direction. The transparent sections are placednear the condensing light point of each unit lens in the lenticular lensmeans. The opaque sections are placed at a peripheral area of thecondensing light point of each unit lens. It is thereby possible toobtain the effect to eliminate the components in an up-and-downdirection and a horizontal direction and to eliminate the occurrence ofa double image and a ghost image.

In the transmission screen according to the present invention, thelouver shaped opaque section in the stray light eliminating means has across section so that a width of the louver shaped opaque section ischanged along the direction of the normal of the outgoing plane of theFresnel lens means. It is thereby possible to obtain the effect toeasily mold the stray light eliminating means and to inject a Chineseink or an ink of another type as the louver shaped opaque section.

In the transmission screen according to the present invention, thelouver shaped opaque section in the stray light eliminating means has across section so that a width of the louver shaped opaque section ischanged along the direction of the normal of the outgoing plane of theFresnel lens means. It is thereby possible to obtain the effect toeasily mold the stray light eliminating means and to inject a Chineseink or another ink as the louver shaped opaque section.

In the transmission screen according to the present invention, the straylight eliminating means is formed in one body on the outgoing plane ofthe Fresnel lens means. It is thereby possible to obtain the effect tosuppress the generation of a reflected ineffective flux of lightgenerated at the outgoing plane of the Fresnel lens means to the minimumstate.

In the transmission screen according to the present invention, the straylight eliminating means is formed in one body on the outgoing plane ofthe Fresnel lens means. It is thereby possible to obtain the effect tosuppress the generation of a reflected ineffective flux of lightgenerated at the outgoing plane of the Fresnel lens means to the minimumstate.

A projection display device according to the present invention has atransmission screen and a projection optical system for projecting lightfluxes to the transmission screen in order to focus an image on thetransmission screen. The transmission screen has Fresnel lens means,stray light eliminating means, and image display means. The Fresnel lensmeans has a Fresnel surface molded at an incident plane thereof forgiving its optical action to projected light fluxes and for outputtingthe light fluxes through its outgoing plane. The stray light eliminatingmeans eliminates a light flux having only a different angle generatedbased on the optical action of the Fresnel surface. The image displaymeans scatters the light flux from the stray light eliminating means tomake the scattered one. It is thereby possible to effect to provide theprojection display device capable of eliminating any occurrence of thegeneration of a double image and a ghost image and of displaying a highquality image.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram to explain a configuration and operation of aconventional refraction Fresnel lens plate.

FIG. 2 is a diagram to explain a configuration and operation of aconventional total reflection Fresnel lens plate.

FIG. 3 is a diagram to explain a configuration and operation of aconventional refraction total reflection Fresnel lens plate.

FIG. 4 is a diagram showing a configuration of a cross section of atransmission screen in an up-and-down direction according to a firstembodiment of the present invention.

FIG. 5 is a diagram showing a configuration of the transmission screenobserved from an oblique direction according to the first embodiment ofthe present invention.

FIG. 6A and FIG. 6B are diagrams showing a configuration of atransmission screen according to a second embodiment of the presentinvention.

FIG. 7A and FIG. 7B are diagrams showing a configuration of atransmission screen according to a third embodiment of the presentinvention.

FIG. 8A to FIG. 8C are diagrams showing a configuration of atransmission screen according to a fourth embodiment of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

The best mode for carrying out the invention will now be described indetail by referring to the accompanying drawings.

FIRST EMBODIMENT

FIG. 4 is a diagram showing a configuration of a cross section of atransmission screen in an up-and-down direction according to a firstembodiment of the present invention. FIG. 5 is a diagram showing aconfiguration of the transmission screen observed from an obliquedirection according to the first embodiment of the present invention.

In FIG. 4, reference character 10C designates a refraction totalreflection Fresnel lens plate (refraction total reflection Fresnel lensmeans), reference number 20 denotes a stray light eliminating plate(stray light eliminating means), and 30 indicates an image display plate(image display means). The transmission screen comprises the refractiontotal reflection Fresnel lens plate 10C, the stray light eliminatingplate 20, and the image display plate 30. Reference character ndesignates the normal which is the common one for the refraction totalreflection Fresnel lens plate 10C, the stray light eliminating plate 20,and the image display plate 30. In FIG. 5, reference number 40designates a projection optical system to output a projected light flux50, and 90 indicates an observer who watches an enlarged display image.

Next, a description will now be given of the operation.

A part of a projected light flux 50, which is output from the projectionoptical system 40 and input to the refraction total reflection Fresnellens plate 10C inclined to the normal n, is refracted at the refractioninclined plane 11 placed at the incident plane of the refraction totalreflection Fresnel lens plate 10C and becomes an effective flux of light53 which is parallel to the normal n. Another part of the projectedlight flux 50 is refracted at the transmission inclined plane 14, thenreflected at the total reflection inclined plane 13 so as to become theeffective flux of light 51 in parallel to the normal n.

The remaining part of the projected light flux 50 other than the abovelight fluxes is refracted at the ineffective facet plane 12 adjacent inposition to the refraction inclined plane 11, or becomes the ineffectiveflux of light 52 (a deviated flux of light) which is inclined to thenormal n after it is refracted at the transmission inclined plane 14 andnot reflected at the total reflection inclined plane 13. In both thecases, the remaining part of the projected light flux 50 then enters theoutgoing plane 15.

The stray light eliminating plate 20 is made up of a condensing lightlens array 21 (condensing light lens array means) formed at the incidentplane side of a transmission substrate 22 (first transmission substrate)and black stripes 23 (first black stripe means) formed at the side ofthe outgoing plane of the transmission substrate 22.

Like the typical configuration shown in FIG. 5, both the condensinglight lens array 21 and the black stripe 23 are made up of a lens arrayin periodically formed in an up-and-down direction andtransparent/opaque lattice plates.

The black stripe 23 is made up of the transparent sections 201 close tothe condensing point of each unit lens forming the condensing light lensarray 21 and the opaque sections 200 at surrounding area of thecondensing point in periodic configuration.

In FIG. 4, the effective fluxes 51 and 53 of light deflected at therefraction total reflection Fresnel lens plate 10C in direction alongthe normal n inputs into the condensing light lens array 21, andcondensed to an area close to the focus of the lens unit of thecondensing light lens array 21, travels through the transparent sections201 and becomes the effective outgoing light 55. The effective outgoinglight 55 is finally input to the image display plate 30. In order toachieve this process, the center of each unit lens of the condensinglight lens array 21 and the center of each transparent section 201 areapproximately equal in position, as shown in FIG. 4 showing a sectionalconfiguration. A lenticular lens 31 (cylindrical lens array andlenticular lens means) is formed in periodic pattern along a horizontaldirection at the incident plane of the image display plate 30.

In addition, the transmission substrate 32 (second transmissionsubstrate) is mounted at the outgoing plane side of the image displayplate 30 in order to hold the lenticular lens 31. The lenticular lens 31has a function to spread the incident light in horizontal direction.

Conventional scattering particles are held in the inside or the areaclose to the surface of the transmission substrate 32.

The transmission substrate 32 acts as the spreading plate in order tofocus the projected image. Accordingly, a light distributioncharacteristic of the image light flux 80 in horizontal direction outputfrom the transmission screen is determined based on the refraction powerof the lenticular lens 31 and the scattering characteristic of thetransmission substrate 32. The light distribution characteristic of theimage light flux 80 in an up-and-down direction is determined based onthe refraction power of the stray light eliminating plate 20 and thescattering characteristic of the transmission substrate 32.

Because both the effective fluxes 51 and 53 of light is deflected indirection along the normal n by the refraction inclined plane 11 and thetotal reflection inclined plane 13.

The image flux 80 output from the transmission screen has a lightdistribution characteristic with a good symmetry to the normal n, sothat the observer 90 at the front position of the transmission screencan watch the image easily.

Next, a description will now be given of the eliminating method of theineffective flux of light from the stray light eliminating plate 20.

The ineffective flux of light 52 generated at the refraction totalreflection Fresnel lens plate 10C is input into the stray lighteliminating plate 20 through the outgoing plane 15 while keeping it inthe inclined state to the normal n. After the ineffective flux of light52 is reflected at the outgoing plane 15 as the reflected ineffectiveflux 54 of light, it is refracted and reflected again by the refractioninclined plane 11, the ineffective facet plane 12, the total reflectioninclined plane 13, and the transmission inclined plane 14 placed at theincident plane side of the refraction total reflection Fresnel lensplate 10C. A part of the light fluxes travels through the outgoing plate15 and then input into the stray light eliminating plate 20 again as theineffective light flux.

According to a detailed light tracing simulation, it is clear that alarge part of the ineffective flux of light which is input again is alight flux greatly inclined to the normal n.

The ineffective flux 52 of light (including the re-input ineffectiveflux of light) which enters to the stray light eliminating plate 20 inan inclined direction to the normal n is absorbed by the opaque sections200 of the black stripe 23 after passing through the condensing lightlens array 21. Accordingly, it is possible to prevent to input it to theimage display plate 30. Thereby, it is possible to greatly improve theconventional problems to eliminate the occurrences of the double imageand the ghost image caused by the ineffective flux 52 of light.

The opaque sections 200 is formed by selecting application andpatterning of well-known various kinds of black color paints, byselecting rough surface working of the outgoing plane of thetransmission substrate 22 or a combination of those processes.

The eliminating function to eliminate the ineffective flux of light bythe stray light eliminating plate 20 used in the present invention isachieved using the condensing light lens array 21 and the black stripes23 formed in a periodic pattern in an up-and-down direction. Thereforeit is possible that the stray light eliminating plate 20 having thisfunction acts the ideal operation when the axis of rotation of therefraction total reflection Fresnel lens plate 10C is positioned on thecenter line of the right section and the left section of thetransmission screen.

Further, the condensing light lens array 21 and the black stripes 23 areformed in a concentric configuration and a periodic structure about thecenter of rotation of the refraction total reflection Fresnel lens plate10C, it is possible to effectively execute the eliminating function toeliminate the ineffective flux of light of the stray light eliminatingplate 20.

In an ideal case, the shading function of the stray light eliminatingplate 20 is originally used when the transmission substrate 22 and thecondensing light lens array 21 do not have any scattering function. Inan usual case, the elements are arranged so that the transmissionsubstrate 32 mainly shares the scattering function to make image.However, it is possible to control the light distribution characteristicand the imaging action for the outgoing light from the transmissionscreen by adding the scattering function to the transmission substrate22 and the condensing light lens array 21 as the components forming thestray light eliminating plate 20.

For example, there is an effective example to prevent the deteriorationof the projected image caused by scintillation generated in the imagelight flux 80. In this example a simple scattering characteristic isapplied to configuration materials forming the transmission substrate 22and the condensing light lens array 21 by adding some fine particles tothem. By this manner, the scattering function is distributed in thedirection of the normal n of the transmission screen in addition to thescattering function of the transmission substrate 32 which is separatedin distance from the stray light eliminating plate 20. It is therefore adesign choice of a system design of the projection display device forthe configuration elements of the stray light eliminating plate 20.

Further, when the thickness of the stray light eliminating plate 20 madeup of the lens array 21, the transmission substrate 22, and the blackstripes 23 is thin and difficult to hold the plate 20 itself, atransmission substrate 24 (a holding transmission substrate) is mounted,as shown by dotted lines in FIG. 4.

Still further, the inventors of the present invention have observed aprojected image using the transmission screen having anotherconfiguration in which the stray light eliminating plate 20 is combinedto the refraction total reflection Fresnel lens plate 10C. This straylight eliminating plate 20 is composed of line-shaped black stripes 23of a periodic form in an up-and-down direction, like the case of theline-shaped condensing lens array 21 of the periodic form in anup-and-down direction shown in FIG. 5. The refraction total reflectionFresnel lens plate 10C is placed on the center line of the transmissionscreen and under the downstream side of the transmission screen.

From a result of the above observation, it is recognized to reduce theoccurrence of the double image and the ghost image, overlapped on thedisplay image, around the area in an up-and-down direction through thecenter of the image. Although the stray light eliminating plate 20 mustbe formed in a concentric circle structure to the center of therefraction total reflection Fresnel lens in an ideal case, the result ofthe above observation means that it is possible to obtain the imagequality improvement effect of not less than a constant level even if thestray light eliminating plate 20 is replaced with the stray lighteliminating plate made up of the condensing light lens array of thestraight-line stripe structure and the black stripe. This replacementwith the stray light eliminating plate greatly relaxes the limitation instructure of the stray light eliminating plate. It is thereby possibleto provide the transmission screen capable of displaying a good imagewith a low cost.

As described above, according to the first embodiment, the transmissionscreen has the refraction total reflection Fresnel lens plate 10C, thecondensing lens array 21, the transparent sections 201, the stray lighteliminating plate 20, and the image display plate 30.

The optical action of the refraction total reflection Fresnel lens plate10C processes the projected light 50 and outputs the processed onethrough the outgoing plane 15 thereof. The condensing light lens array21 is composed of the unit lenses arranged of a periodic structure in anup-and-down direction at the incident plane of the transmissionsubstrate 22.

The transparent sections 201 are mounted at the area close to the focuspoint of each unit lens.

The stray light eliminating plate 20 is composed of the opaque sections200 formed close to the condensing light point of each unit lens and theblack stripes 23 arranged alternately to each other in a periodicstructure in an up-and-down direction at the outgoing plane of thetransmission substrate 22.

The image display plate 30 is composed of the lenticular lens 31 havingthe unit lenses in periodic pattern in horizontal direction on theincident plane of the transmission substrate 32 which scatters the lightflux based on its scattering characteristic. It is thereby possible toprovide the transmission screen capable of displaying the normalprojected image with a high quality only using the effective lightfluxes 51 and 53.

In addition, according to the first embodiment, the refraction inclinedplane 11 in the refraction total reflection Fresnel lens plate 10Crefracts the projected light flux 50 toward approximately paralleldirection to the normal n of the outgoing plane 15. The total reflectioninclined plane 13 on the refraction total reflection Fresnel lens plate10C reflects the light flux refracted at the transmission inclined plane14 toward the approximately parallel direction to the normal n of theoutgoing plane 15. It is thereby possible to form the display image of alight distribution characteristic of symmetry to the normal n of thetransmission screen, and to display the image with the optimum conditionto the observer 90 positioned at the center of the transmission screen.

Still further, according to the first embodiment, the stray lighteliminating plate 20 has the transmission substrate 24 to hold thetransmission substrate 22, the condensing light lens array 21, and theblack stripes 23. It is possible to obtain the effect to form the straylight eliminating plate 20 even if the thickness of the layer composedof the transmission substrate 22, the condensing light lens array 21,and the black stripes 23 is thin.

Furthermore, according to the first embodiment, the stray lighteliminating plate 20 has the condensing light lens array and the firstblack stripes molded with a periodic structure in a concentric circle tothe center of rotation of the Fresnel lens plate 10C. It is therebypossible to obtain the effect that the stray light eliminating plate 20can perform its ineffective light flux eliminating function moreeffectively.

Still furthermore, according to the first embodiment, the stray lighteliminating plate 20 has the condensing light lens array and the firstblack stripes molded in a periodic structure of a straight-line shaped.It is thereby possible to obtain the effect to greatly relax thelimitation of the manufacturing for the stray light eliminating plate 20and to display the good image with a low cost.

Moreover, according to the first embodiment, the stray light eliminatingplate 20 has the transmission substrate 22 with the scatteringcharacteristic and the condensing light lens array 21 with thescattering characteristic. It is possible to obtain the effect toprevent the deterioration of the projected image caused by thescintillation generated in the projected image 80.

Still moreover, according to the first embodiment, the projectiondisplay device has the projection optical system 40 to display the imageon the transmission screen by projecting the projected light flux 50 tothe transmission screen. The embodiment has the effect that it ispossible to provide the projection display device capable of displayinghigh quality images by eliminating the occurrence of the double imageand the ghost image.

SECOND EMBODIMENT

The second embodiment shows how to reduce the occurrence of a doubleimage and a ghost image generated in a wide area including the projectedimage area.

FIG. 6A and FIG. 6B are diagrams showing a structure of the transmissionscreen according to the second embodiment of the present invention. InFIG. 6A and FIG. 6B, reference number 33 designates a transmissionsubstrate (a third transmission substrate), and 34 denotes black stripes(second black stripe means). In FIG. 6, the image display plate 30 hasthe function to eliminate the horizontal component of the ineffectiveflux of light, instead of the stray light eliminating plate 20. In orderto achieve this feature, the black stripes 34 and the transmissionsubstrate 33 are placed between the lenticular lens 31 and thetransmission substrate 32 of the periodic pattern in horizontaldirection. Because other components are the same as those of the caseshown in FIG. 4 and FIG. 5, the explanation for the same configurationis omitted here.

FIG. 6B shows an enlarged view of the image display plate 30 shown inFIG. 6A.

In order to form the projected image, like the case of the firstembodiment shown in FIG. 5, scattering particles are dispersed and heldin the internal area or at the area around the surface of thetransmission substrate 32. This configuration gives the scatteringcharacteristic to the transmission substrate 32. The lenticular lens 31is a cylindrical shaped lens array which draws in an up-and-downdirection and has a periodic pattern in horizontal direction.

Further, the black stripes 34 has the periodic structure in horizontaldirection so that the opaque sections 300 are shifted from the center ofthe lens by matching the transparent section 301 to the center of eachunit lens of the lenticular lens 31. Further, the opaque sections 300has been made by one of or a combination of a well-known selectiveapplication for each kind of black color prints, a patterning, and aselective rough surface work for the surface of the outgoing side of thetransmission substrate 33.

The black stripes 34 and the lenticular lens 31 are held with a desireddistance between the transmission substrate 33 and the black stripes 34are bonded to the transmission substrate 32.

The formation of the image display plate 30 with the above describedmanner can achieve that the image display plate 30 has the function toeliminate the ineffective flux of light in horizontal direction based onthe same principle of the stray light eliminating plate 20 shown in FIG.5.

When the symmetric axis of rotation is on the center line of thetransmission screen and the refraction total reflection Fresnel lensplate 10C is placed at the area close to the lower section of thetransmission screen, the stray light eliminating plate 20 can eliminatethe ineffective flux of light generated in the up-and-down direction ofthe area close to the center section in the horizontal direction of thetransmission screen. The combination of the stray light eliminatingplate 20 and the image display plate 30 can eliminate the ineffectiveflux of light generated in an inclined direction of the area outside ofthe center of the transmission screen in right and left directions. Itis thereby possible to more strictly eliminate the double image and theghost image when compared with the case shown in FIG. 4 and FIG. 5.

As described above, according to the second embodiment, the imagedisplay plate 30 has the black stripes 34 formed between thetransmission substrate 32 and the lenticular lens 31. The black stripes34 are so formed that the transparent sections 301 and the opaquesections 300 are alternately formed at the outgoing plane of thetransmission substrate 33 in a periodic pattern in the horizontaldirection. The black stripes 34 are formed at the area close to thecondensing point of each unit lens of the lenticular lens 31. The opaquesections 300 are formed at the peripheral area of the condensing pointof each unit lens. This configuration has the effect to eliminate thecomponents in an up-and-down direction and the horizontal direction ofthe ineffective flux of light 52. It is thereby possible to eliminatethe double image and the ghost image more strictly.

THIRD EMBODIMENT

A third embodiment will explain a modification example of theconfiguration of the transmission screen capable of eliminating both thecomponents in an up-and-down direction and a horizontal direction of theineffective flux of light, like the case of the second embodiment.

FIG. 7A and FIG. 7B are diagrams showing a configuration of thetransmission screen of the third embodiment of the present invention.

In FIG. 7A, reference character 10C designates a refraction totalreflection Fresnel lens plate like that shown in FIG. 4, referencenumber 20 denotes a stray light eliminating plate placed at the outgoingplane 15 side of the refraction total reflection Fresnel lens plate 10C,and 26 indicates transparent sections of the stray light eliminatingplate 20.

Reference number 25 designates louver shaped opaque sections in thestray light eliminating plate 20, and 55 denotes an effective outgoinglight flux of the stray light eliminating plate 20. The image displayplate 30 has the same configuration shown in FIG. 4. Further, FIG. 7Bshows an enlarged oblique view of the stray light eliminating plate 20and the refraction total reflection Fresnel lens plate 10C observed fromthe effective outgoing light flux 55 side. In this enlarged obliqueview, reference character 25H designates the louver shaped opaquesections in a horizontal direction, which are arranged in a periodicform in an up-and-down direction between the transparent sections 26.Reference character 25V denotes the louver shaped opaque sections in anup-and-down direction formed in a periodic pattern between thetransparent sections 26 in the horizontal section.

Next, a description will now be given of the operation of thetransmission screen shown in FIG. 7.

In the same manner shown in FIG. 4, by the refraction action of therefraction inclined plane 11 and the actions of the transmissioninclined plane 14, and the total reflection inclined plane 13, aprojected light flux 50 becomes the effective fluxes 53 and 51 of lightwhich travel in the direction of the normal n of the transmissionscreen. The effective fluxes 53 and 51 of light pass through thetransparent sections 26 and input as the effective outgoing light fluxes55 into the image display plate 30. The light fluxes 55 are scattered bythe lenticular lens 31 in a horizontal direction and the scattered lightfluxes are then displayed as the projected image on the transmissionsubstrate 32 having the scattering characteristic.

A light distribution characteristic of the image light flux 80 in ahorizontal direction is determined based on the scatteringcharacteristic of the lenticular lens 31 in an horizontal direction andthe scattering characteristic of the transmission substrate 32.

The arrow with dotted lines designated by reference number 52 indicatesan ineffective flux of light passed through the ineffective facet plane12 of the refraction total reflection Fresnel lens plate 10C or anineffective flux of light which is not reflected by the total reflectioninclined plane 13 after passed through the transmission inclined plane14.

This ineffective flux of light 52 is absorbed by the louver shapedopaque sections 25 placed along the direction of the normal n, or whichbecomes the reflected ineffective flux of light 54 after it is reflectedat the boundary surface of the refraction total reflection Fresnel lensplate 10C and the stray light eliminating plate 20. After this, thereflected ineffective flux of light 54 at the boundary surface 15 isrefracted and reflected by the refraction inclined plane 11, theineffective facet plane 12, the total reflection inclined plane 13, thetransmission inclined plane 14 at the incident side of the refractiontotal reflection Fresnel lens plate 10C, and then enters again into theboundary surface 15, and a large part thereof is absorbed by the louvershaped opaque section 52.

It is not necessary to consider any generation of the refractedineffective light flux 54 because the boundary surface 15 seldomgenerates the reflection ineffective flux of light 54 in cases where thestray light eliminating plate 20 is formed in one body on the bottomsurface (as the outgoing plane) of the refraction total reflectionFresnel lens plate 10C or both are bonded with an adhesive material.

It is possible to form the stray light eliminating plate 20 using acrylmaterial, for example, lattice shaped grooves are formed using a die inwhich projecting rows corresponding to the louver shaped opaque sections25 are formed and a Chinese ink or another ink with an absorptiveproperty is then poured into the groove sections.

When the Chinese ink or another ink is poured, dusts remained on thesurface of the stray light eliminating plate 20 are eliminated asnecessary in order to keep the transmission characteristic of thetransparent sections 26.

The stray light eliminating plate 20 formed by the above manner isbounded in one body onto the refraction total reflection Fresnel lensplate 10C made up of acryl material with an adhesive material having asame refraction index of the acryl material, for example. It is therebypossible to minimize the generation of the reflected ineffective flux oflight 54. It is of course acceptable to form it by making of one piecethe stray light eliminating plate 20 directly on the bottom surface ofthe refraction total reflection Fresnel lens plate 10C and then byinjecting the Chinese ink or another ink into it.

Although FIG. 7A shows the sectional view of the transmission screen inan up-and-down direction, the projected light flux 50 has an inclinedcomponent and a horizontal component. In this case, the horizontalcomponent of the ineffective flux of light generated is mainly absorbedby the louver shaped opaque sections 25V in an up-and-down direction. Inaddition, the component of the ineffective flux of light in theup-and-down direction is mainly absorbed by the louver shaped opaquesections 25H in the horizontal direction.

It is also acceptable for the louver shaped opaque sections 25, 25V, and25H to have a shape whose width is gradually changed toward thedirection of the normal n in consideration of an easily pattern-moldingcharacteristic and an easy injecting characteristic of the Chinese inkor an ink of another type.

In this case, the louver shaped opaque sections 25 become a trapezoidalshape (omitted from the diagram) whose width is gradually changed towardthe normal n in the sectional view of the transmission screen shown inFIG. 7A.

As described above, according to the third embodiment, the stray lighteliminating plate 20 is composed of the transparent sections 26 whichtransmit light fluxes, the louver shaped opaque sections 25H in anhorizontal direction arranged between the transparent sections 26 in aperiodic structure in an up-and-down direction, and the louver shapedopaque sections 25V in an up-and-down direction arranged between thetransparent sections 26 in a periodic structure in a horizontaldirection. It is thereby possible to eliminate the components of theineffective flux of light 52 in the up-and-down direction and in thehorizontal direction. This can obtain the effect to eliminate the doubleimage and the ghost image more strictly.

In addition, according to the third embodiment, the stray lighteliminating plate 20 is so formed that the width of each of the crosssectional shape of the louver shaped opaque sections 25H and 25V ischanged along the normal n of the outgoing plane 15 of the Fresnel lensplate 10C. It is thereby possible to obtain the effect to easily injectthe Chinese ink or an ink of another type for the formation of the moldof the stray light eliminating plate 20 and the louver shaped opaquesections.

Still further, according to the third embodiment, the stray lighteliminating plate 20 and the outgoing plane 15 of the Fresnel lens plane10C are formed in one body, it is possible to minimize the generation ofthe reflection ineffective flux of light generated at the outgoing planeof the Fresnel lens plate 10C.

FOURTH EMBODIMENT

FIG. 8 shows an example of a configuration to eliminate both thecomponents in an up-and-down direction and a horizontal direction of theineffective flux of light by combining the louver elements andlenticular lenses with black stripes.

FIG. 8A, FIG. 8B, and FIG. 8C are diagrams showing a configuration of atransmission screen of the fourth embodiment of the present invention.

In FIG. 8A to FIG. 8C, reference number 20 designates a stray lighteliminating plate composed of louver shaped opaque sections 25 andtransparent sections 26. As shown in FIG. 8B, the louver shaped opaquesections 25 are composed only of the horizontal louver shaped opaquesections 25H arranged in a periodic pattern in an up-and-down direction.

The image display plate 30 is composed of various layers such as thelenticular lens 31, the transmission substrate 33, the black stripe 34,and the transmission substrate 32 which are laminated in order observedfrom the incident side of the effective outgoing light flux 55. As shownin the enlarged view of FIG. 8C, the black stripes 34 are composed ofthe stripe shaped opaque sections 300 and the transparent sections 301arranged in a periodic pattern in a horizontal direction.

The center section of the transparent section 301 in the horizontaldirection is placed so that it is matched to the center of each unitlens in the lenticular lens 31. The transmission substrate 33 keeps afixed distance between the lenticular lens 31 and the black stripe 34.

The refraction total reflection Fresnel lens plate 10C has the sameconfiguration of that shown in FIG. 4. The explanation thereof isomitted here.

Next, a description will be given of the operation of the transmissionscreen shown in FIG. 8.

In the same manner shown in FIG. 4, the projected light flux 50 becomesthe effective fluxes 53 and 51 of light traveling toward the normal n ofthe transmission screen by the refraction action of the refractioninclined plane 11, the actions of the transmission inclined plane 14 andthe total reflection inclined plane 13.

After passing through the transparent sections, the effective fluxes 53and 51 of light become the effective outgoing light flux 55 and inputinto the image display plate 30. After the scattering in the horizontaldirection, the scattered light flux is focused onto the transmissionsubstrate 32 of the scattering characteristic and the projected image isthereby made on it.

The light distribution characteristic of the image light flux 80 in ahorizontal direction is determined based on the refractioncharacteristic of the lenticular lens 31 and the scatteringcharacteristic of the transmission substrate 32.

The light distribution characteristic in an up-and-down direction isdetermined based on the scattering characteristic of the transmissionsubstrate 32.

The arrow with dotted lines designated by reference number 52 indicatesan ineffective flux of light passed through the ineffective facet plane12 of the refraction total reflection Fresnel lens plate 10C or anineffective flux of light which is not reflected by the total reflectioninclined plane 13 after passed through the transmission inclined plane14.

This ineffective flux of light 52 is absorbed by the louver shapedopaque sections 25 placed along the direction of the normal n, orbecomes the reflected ineffective flux of light 54 reflected at theboundary surface 15 of the refraction total reflection Fresnel lensplate 10C and the stray light eliminating plate 20.

After this, the reflected ineffective flux of light 54 is refracted andreflected by the refraction inclined plane 11, the ineffective facetplane 12, the total reflection inclined plane 13, the transmissioninclined plane 14 at the incident side of the refraction totalreflection Fresnel lens plate 10C, and then enters again into theboundary surface 15, and a large part thereof is absorbed by the louvershaped opaque section 52.

It is not necessary to consider any generation of the refletedineffective light flux 54 by the boundary surface 15 because theboundary surface 15 seldom generates the reflected ineffective lightflux 54 in cases where the stray light eliminating plate 20 and therefraction total reflection Fresnel lens plate 10C are formed in onebody on the bottom surface (as the outgoing plane) or both are bondedwith an adhesive material.

It is possible to form the stray light eliminating plate 20 using acrylmaterial, for example, lattice shaped grooves are formed using a die inwhich projecting rows corresponding to the louver shaped opaque sections25 are formed and a Chinese ink or an ink of another type with anabsorptive property is then poured into the groove sections.

When the Chinese ink or the ink of another type is poured, dustsremained on the surface of the stray light eliminating plate areeliminated as necessary in order to keep the transmission characteristicof the transparent sections 26.

The stray light eliminating plate 20 formed by the above manner isbonded in one body onto the refraction total reflection Fresnel lensplate 10C made up of acryl material with an adhesive material having asame refraction index of the acryl material, for example. It is therebypossible to minimize the generation of the reflected ineffective flux oflight 54. It is of course acceptable to form it by making of one piecethe stray light eliminating plate 20 directly on the bottom surface ofthe refraction total reflection Fresnel lens plate 10C and then byinjecting the Chinese ink or the ink of another type into it.

It is also acceptable for the louver shaped opaque sections 25 and 25Vto have a shape whose width is gradually changed toward the direction ofthe normal n in consideration of an easily pattern-moldingcharacteristic and an easy injecting characteristic of the Chinese inkor an ink of another type.

In this case, the louver shaped opaque sections 25 become a trapezoidalshape (omitted from the diagram) whose width is gradually changed towardthe normal n in the sectional view of the transmission screen shown inFIG. 8A.

Although FIG. 8A shows the sectional view of the transmission screen inan up-and-down direction, the projected light flux 50 has an inclinedcomponent and a horizontal component. In this case, the horizontalcomponent of the ineffective flux of light generated in this case ismainly absorbed by the action of the opaque sections 300 in thelenticular lens 31 and the black stripes 34 in the image display plate30 (see FIG. 8C).

In addition, both the lenticular lenses 31 and the black stripes 34 arearranged in a periodic pattern in a horizontal direction and have thesame principle to absorb the ineffective flux of light in the case shownin FIG. 4 where both the condensing light lens array 21 and the blackstripes 23 are rotated in angle by 90 degrees when compared with thecase shown in FIG. 8C.

In addition, the component of the ineffective flux of light in theup-and-down direction is mainly absorbed by the louver shaped opaquesections 25H in the horizontal direction (see FIG. 8C).

As described above, according to the fourth embodiment, the stray lighteliminating plate 20 is composed of the transparent sections 26 passinglight fluxes and the horizontal louver shaped opaque sections 25Harranged in a periodic structure in an up-and-down direction between thetransparent sections. The image display plate 30 has the black stripes34 formed between the transmission substrate 32 and the lenticularlenses 31. The black stripes 34 is composed of the transparent sections301 and the opaque sections 300 which are alternately arranged at theoutgoing plane of the transmission substrate 33 in a periodic structurein the horizontal direction. The transparent sections 301 are placednear the condensing points of unit lenses in the lenticular lenses 31.The opaque sections 300 are placed at the peripheral area of thecondensing positions of the unit lenses. This can eliminate thecomponents of the ineffective flux of light 52 in the up-and-downdirection and the horizontal direction. It is possible to obtain theeffect to eliminate the double image and the ghost image more strictly.

In addition, according to the fourth embodiment, the stray lighteliminating plate 20 is so formed that the width of each of the crosssectional shape of the louver shaped opaque sections 25H is changedalong the normal n of the outgoing plane 15 of the Fresnel lens plate10C. It is thereby possible to obtain the effect to easily inject theChinese ink or an ink of another type for the formation of the mold ofthe stray light eliminating plate 20 and the louver shaped opaquesections.

Still further, according to the fourth embodiment, the stray lighteliminating plate 20 and the outgoing plane 15 of the Fresnel lens plane10C are formed in one body, it is possible to minimize the occurrence ofthe reflection ineffective flux of light generated at the outgoing planeof the Fresnel lens plate 10C.

Each of the embodiments shown in FIG. 4 to FIG. 8 has shown theconfiguration and the operation of the transmission screen with therefraction total reflection Fresnel lens plate 10C.

However, it is also possible to obtain the same effect even if followingtransmission screens using Flesnel lens plates (1) to (3) instead of therefraction total reflection Fresnel lens plates 10C shown in FIG. 4 toFIG. 8.

(1) A transmission screen having the refraction Fresnel lens plate (seeFIG. 1) in which a refraction Fresnel lens plate composed of therefraction inclined plane and the ineffective facet plane in a periodicstructure is formed at the incident plane side thereof;

(2) A transmission screen having the total reflection Fresnel lens plate(see FIG. 2) in which a total reflection Fresnel surface composed of atotal reflection inclined surface and a transmission inclined surface ina periodic structure is formed at the incident plane side thereof; and

(3) A transmission screen having a refraction total reflection Fresnellens plate of a hybrid structure including three areas of a small radiusarea, a large radius area, and a very large area because this refractiontotal reflection Fresnel lens plate has a concentric circle structure.In the small area, in order to increase a transmission efficiency theratio of a refraction Fresnel section composed of a refraction inclinedplane and an ineffective facet surface to a total reflection Fresnelsection composed of a total reflection inclined plane and a transmissioninclined plane is increased. In the large radius area, the transmissionefficiency is gradually increased by increasing the ratio of the totalreflection Fresnel section. The very large area is composed of only thetotal reflection Fresnel lens section in order to obtain the hightransmission efficiency.

INDUSTRIAL APPLICABILITY

As set forth, the transmission screen according to the present inventionis suitable for a projection system to display high quality images.

1. A transmission screen comprising: Fresnel lens means having a Fresnelsurface molded as an incident plane thereof for giving its opticalaction to projected light fluxes, and for outputting the light fluxesthrough an outgoing plane thereof; stray light eliminating means foreliminating an ineffective light flux generated based on the opticalaction of the Fresnel surface; and image display means for focusing thelight flux from the stray light eliminating means and controlling thelight flux distribution characteristic.
 2. The transmission screenaccording to claim 1, wherein the Fresnel lens means is refractionFresnel lens means having a refraction Fresnel plane formed at theincident plane thereof, and the refraction Fresnel plane comprises:refraction inclined planes for refracting light fluxes; and ineffectivefacet planes, which are arranged in a periodic structure.
 3. Thetransmission screen according to claim 1, wherein the Fresnel lens meansis total reflection Fresnel lens means having a total reflection Fresnelplane formed at the incident plane thereof, and the total reflectionFresnel plane comprises: transmission inclined planes for refractinglight fluxes; and total reflection inclined planes for reflecting thelight fluxes refracted at the transmission inclined planes, which arearranged in a periodic structure.
 4. The transmission screen accordingto claim 1, wherein the Fresnel lens means is refraction totalreflection Fresnel lens means having a refraction total reflectionFresnel plane formed at the incident plane thereof, and the refractiontotal reflection Fresnel plane comprises: refraction inclined planes forrefracting light fluxes; ineffective facet planes; transmission inclinedplanes for refracting the light fluxes; and total reflection inclinedplanes for reflecting the light fluxes refracted at the transmissioninclined planes, which are arranged in a periodic structure.
 5. Thetransmission screen according to claim 2, wherein the refractioninclined planes in the Fresnel lens means refract the projected lightfluxes toward a direction approximately parallel to a normal of theoutgoing plane of the Fresnel lens means.
 6. The transmission screenaccording to claim 3, wherein the total reflection inclined planes inthe Fresnel lens means reflect the light fluxes refracted at thetransmission inclined planes toward a direction approximately parallelto a normal of the outgoing plane of the Fresnel lens means.
 7. Thetransmission screen according to claim 4, wherein the refractioninclined planes in the Fresnel lens means refract the projected lightfluxes toward a direction approximately parallel to a normal of theoutgoing plane of the Fresnel lens means, and the total reflectioninclined planes in the Fresnel lens means reflect the light fluxesrefracted at the transmission inclined planes toward the directionapproximately parallel to the normal of the outgoing plane of theFresnel lens means.
 8. The transmission screen according to claim 4,wherein the Fresnel lens means changes a ratio of a total reflectionFresnel section and a refraction Fresnel section, and the totalreflection Fresnel section is composed of the transmission inclinedplanes and the total reflection inclined planes and the refractionFresnel section is composed of the refraction inclined planes and theineffective facet planes according to a distance measured from a centerof its rotation.
 9. The transmission screen according to claim 1,wherein the stray light eliminating means comprises: condensing lightlens array means in which unit lenses are arranged at an incident planeof a first transmission substrate in a periodic structure in anup-and-down direction; and first black stripe means composed oftransparent sections placed near a condensing light point of each unitlens and opaque sections placed at a peripheral area of the condensinglight point of each unit lens, which are arranged alternately at theoutgoing plane of the first transparent substrate in a periodicstructure in an up-and-down direction.
 10. The transmission screenaccording to claim 1, wherein the image display means is lenticular lensmeans having the unit lenses arranged in a periodic structure in ahorizontal direction at an incident plane of a second transparentsubstrate having a scattering characteristic capable of scattering thelight fluxes.
 11. The transmission screen according to claim 9, whereinthe stray light eliminating means comprises: a holding transmissionsubstrate for holding the first transmission substrate; the condensinglight lens array means; and the first black stripe means.
 12. Thetransmission screen according to claim 9, wherein the stray lighteliminating means comprises: the condensing light lens array means; andthe first black stripe means, which are molded with a concentric circleshape around a center of rotation of the Fresnel lens means.
 13. Thetransmission screen according to claim 9, wherein the stray lighteliminating means comprises: the condensing light lens array means; andthe first black stripe means, which are molded with a periodic structureof a line shape.
 14. The transmission screen according to claim 9,wherein the stray light eliminating means comprises: one of the firsttransmission substrate having a scattering characteristic; and thecondensing light lens array means having the scattering characteristic.15. The transmission screen according to claim 10, wherein the imagedisplay means comprises: second black stripe means in which transparentsections and opaque sections are arranged at the outgoing plane of athird transparent substrate alternately in a periodic structure in ahorizontal direction, the transparent sections are placed near thecondensing light point of each unit lens in the lenticular lens means,and the opaque sections are placed at a peripheral area of thecondensing light point of each unit lens.
 16. The transmission screenaccording to claim 1, wherein the stray light eliminating meanscomprises: transparent sections through which the light fluxes pass;horizontal louver shaped opaque sections arranged in a periodicstructure in an up-and-down direction between the transparent sections;and up-and-down louver shaped opaque sections arranged in a periodicstructure in a horizontal direction between the transparent sections.17. The transmission screen according to claim 10, wherein the straylight eliminating means comprises: transparent sections through whichthe light fluxes pass; and a horizontal louver shaped opaque sectionsarranged in a periodic structure in an up-and-down direction between thetransparent sections, and the image display means comprises second blackstripe means in which transparent sections and opaque sections arearranged at the outgoing plane of a third transparent substratealternately in a periodic structure in a horizontal direction, thetransparent sections are placed near the condensing light point of eachunit lens in the lenticular lens means, and the opaque sections areplaced at a peripheral area of the condensing light point of each unitlens.
 18. The transmission screen according to claim 16, wherein thelouver shaped opaque section in the stray light eliminating means has across section so that a width of the louver shaped opaque section ischanged along the direction of the normal of the outgoing plane of theFresnel lens means.
 19. The transmission screen according to claim 17,wherein the louver shaped opaque section in the stray light eliminatingmeans has a cross section so that a width of the louver shaped opaquesection is changed along the direction of the normal of the outgoingplane of the Fresnel lens means.
 20. A projection display devicecomprising: a transmission screen; and a projection optical system forprojecting light fluxes to the transmission screen in order to focus animage on the transmission screen, wherein the transmission screencomprises: Fresnel lens means having a Fresnel surface molded at anincident plane thereof for giving its optical action to projected lightfluxes and for outputting the light fluxes through its outgoing plane;stray light eliminating means for eliminating an ineffective light fluxgenerated based on the optical action of the Fresnel surface; and imagedisplay means for focusing the light flux from the stray lighteliminating means and controlling the light flux distributioncharacteristic.
 21. A light transmission apparatus, comprising: aFresnel lens having a Fresnel surface as an incident plane thereof, anddirecting an incoming light flux; a stray light eliminating plate whichreceives a light flux from the Fresnel lens, wherein the stray lighteliminating plate eliminates a vertical component of ineffective lightflux, and further comprises, a condensing light lens array periodic in avertical direction which focuses the light flux received from theFresnel lens, a transmission substrate which receives the focused lightflux from the condensing light array, and a plurality of black stripesassociated with the outgoing side of the transmission substrate whichare arranged to block the vertical component of ineffective light flux;and an image display plate which receives a light flux from the straylight eliminating plate, wherein the image display plate eliminates ahorizontal component of ineffective light flux.
 22. A light transmissionapparatus, comprising: a Fresnel lens having a Fresnel surface as anincident plane thereof, and directing an incoming light flux; a straylight eliminating plate which receives a light flux from the Fresnellens, wherein the stray light eliminating plate eliminates a verticalcomponent of ineffective light flux; and an image display plate whichreceives a light flux from the stray light eliminating plate, whereinthe image display plate eliminates a horizontal component of ineffectivelight flux and further comprises a condensing light lens array periodicin the horizontal direction which focuses the light flux received fromthe stray light eliminating plate, a first transmission substrate whichreceives the focused light flux from the condensing light lens array, aplurality of black stripes associated with the outgoing side of thefirst transmission substrate which are arranged to block the horizontalcomponent of ineffective light by opaque sections, and a secondtransmission substrate which receives light flux through transparentsections of the plurality of black stripes.